I had the same issue but the problem was that I didn't understand how it's supposed to work rather than it being broken.
When you press the Emoji annotation shortcut key (e.g. Ctrl+. as configured by ibus-setup), the "e̲" character that's inserted into the text signals that you have switched from the regular mode to the emoji inserting mode. Press it again or Esc to switch back to the regular mode and the "e̲" character disappears.
To insert an emoji, you can use it in two ways:
1. Select an emoji from the list (Emoji selector dialog)
- Press the Emoji annotation shortcut (Ctrl+.) to switch to the emoji inserting mode - the character "e̲" is inserted
- Press Ctrl+Space to open the emoji group selector
- Using the keyboard, select a group and press Enter to switch to the emoji selector view
- Select an emoji and press Enter to insert it into the text and switch back to the regular mode (the "e̲" character will be replaced by the selected emoji character)
2. Type the name or shorthand of the emoji to be inserted
- Press the Emoji annotation shortcut (Ctrl+.) to switch to the emoji inserting mode - the character "e̲" is inserted
- Type the emoji name or its textual representation, e.g.
:) or heart
- Press Ctrl+Space to replace the inserted text with the emoji corresponding to the inserted text (the "e̲" character stays there at this point)
- If you're OK with the inserted emoji, press Enter to switch back to the regular mode (the "e̲" character disappears and the inserted emoji stays in the text)
- If you don't like the inserted emoji, you can go back to the inserted text by pressing Escape (press it again to cancel the emoji mode completely - inserted text including the "e̲" character is removed and you switch back to the regular mode) or you can press Ctrl+Space again to show the emoji selector with emojis filtered by the inserted text, select the emoji you like and press Enter to insert it to the text and switch back to the regular mode
Disclaimer: I have just discovered how it works so it's possible that my description is incomplete or inaccurate.